Many people suffer from frequent lapses in mental acuity and alertness during normal waking activities. Whether symptomatic of a clinical disorder or a debilitating lifestyle factor, this problem leads to errors in decision-making and performance, reduces productivity, and increases the likelihood of accidents. Such attention lapses are common during motor vehicle operation, and the incidence of collisions is much higher in individuals with abnormal sleep patterns than in others. The impact of medical treatments on the ability to maintain alertness during daily activities is typically only assessed via the patient's subjective reports and questionnaire responses, or sometimes by repetitive psychometric laboratory tasks that lack environmental validity. There is a critical need for improved, objective methods for tracking the capacity to sustain concentration on the routine yet sometimes demanding behaviors of everyday life. This Phase II project aims to further develop and evaluate the Functional Alertness Driving Evaluation (FADE), a system for measuring treatment-related changes in the ability to consistently pay attention during driving behaviors. A large body of research indicates that neurophysiologic measures can provide direct evidence regarding the degree to which attention and mental effort are engaged by a task, information that cannot be directly inferred from overt performance. The FADE will complement behavioral measures with a fully-automated multivariate analysis of neurophysiological signals recorded during operation of a driving simulator in a laboratory or sleep clinic. Preliminary work demonstrated the feasibility of measuring the deleterious effects of sleep deprivation on subjects operating a flight simulator program, and of automatically detecting inattentiveness in subjects operating a driving simulator. This project also builds on our related success in developing the first automated neurocognitive testing system that combines psychometric task performance with brain function measures. That existing system will provide a technological infrastructure for the FADE. In Phase II we will refine our testing and analysis procedures, implement a prototype system, and validate the methods in the context of laboratory studies of altered alertness and in clinical research on the neurocognitive effects of CPAP treatment in patients.